δ13C and δ15N of plants in a longitudinal transect from the Andes to the Atlantic coast: Terrestrial baseline for paleodietary and paleocological studies

•δ13C and δ15N variability in modern plants from the Atlantic coast to the Andes.•δ13C and δ15N values of plants settle a baseline for isotopic studies of Patagonia.•Agreement between the isotopic variations recorded in plants and herbivores.•Isotopic variability provides opportunities to investigate use of space and mobility.